How much does ESP and traction control really help? This will be my first winter driving an 08 plate mondeo with both.
They help, but not against the laws of physics. If you have winter tyres and are driving at below highway speeds then it's very hard to loose control over the car, unless driving on pure ice. Traction control helps with taking off, but again - tyres. Traction control won't help much on ice with summer tyres. If you switch it on the car won't allow you to rev high enough to even get going and if you turn it off then you will spin the weels.
ESP helps with the sideways motion, it brakes 1 wheel to force the car to go where your wheels are turning. If you're going 50mph to a corner then not much help, but at lower speeds and on reasonable road conditions it's a real lifesaver. Can be forced to do some tricks too.
For example on a front-wheel drive car it is possible with ESP to force a powerslide similar to a rear-wheel drive car. It breaks the inner rear wheel acting like a mini-handbrake.
I've driven one with both and have pushed it to the limit in winter conditions. At about 45mph I started turning the wheel left-and-right rapidly, the car swung sideways a couple of times but always remained where I pointed the wheels, very good.